JP2008094894A - Ink set, method of inkjet-recording, ink cartridge, recording unit, and inkjet-recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink set inhibiting both of the development of a specific micro-beading phenomenon and a beading phenomenon occurring in a pigment ink on forming a second color or third color image by using a light black, light cyan and/or light magenta. <P>SOLUTION: This ink set is characterized by being constituted by the light black ink having a specific composition containing a nonionic surfactant and water soluble compound, and a light cyan ink and/or light magenta ink having a specific composition containing the nonionic surfactant and water soluble compound, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink set comprising a combination of light black ink and light cyan ink and / or light magenta ink. Furthermore, the present invention relates to an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus using the ink set.

  The ink jet recording method performs recording by causing ink droplets to fly and attaching ink to a recording medium such as paper. In particular, according to the ink jet recording method in which ink is ejected by the action of thermal energy, a high-density multi-orifice of the recording head can be easily realized, and high-resolution and high-quality images can be recorded at high speed. can do.

  In recent years, inks that can be used in various applications using these techniques have been demanded. In particular, pigment inks are used in applications that emphasize image fastness. Even in the use of these pigment inks, it is required not only to form a beautiful colored image but also to form a gradation of a monochrome image and a beautiful halftone.

  In order to satisfy these requirements, conventionally, a plurality of black inks having different carbon black contents have been used. In the present invention, an ink having a small carbon black content as used in this case is called a light black ink. As a result, it is said that the color reproducibility with respect to dark colors such as shadow portions, the improvement of gray gradation, the stability of gray balance, and metamerism can be eliminated (see Patent Documents 1 and 2).

  In addition, for the purpose of improving several problems in dark and light pigment inks including black and light black, for example, penetrability and fixability, an ink set is proposed in which the surface tension of light ink is lower than that of dark ink. (See Patent Document 3). In addition, for the purpose of improving the color developability and scratch resistance of the obtained image, there is a proposal for including polymer fine particles only in a light ink among a plurality of inks constituting an ink set (Patent Document 4). reference). Furthermore, for the purpose of suppressing the occurrence of color bleeding, feathering, and color bleeding, it has been proposed that at least one of the light-colored inks contains a saccharide (see Patent Document 5).

  In addition, for the purpose of reducing reddishness, yellowishness, reduction of golden gloss phenomenon, phase shift, and further gray balance stability and metamerism, at least three types of black inks with different contents should be used as a set. (See Patent Documents 6 to 9). Further, in the proposal in which two or more kinds of light black inks are added to the ink constituting the ink set, the following studies are performed. For example, ink containing another color material in addition to carbon black is used, or light cyan or light magenta, which has a relatively small pigment content compared to normal dark cyan or dark magenta, is added to the ink constituting the ink set. Has been done. And, by adding ink of red, green, violet, orange to the ink constituting the ink set, or using ink with resin emulsion added, the effect of improving the color and hue can be obtained. There is a description.

Japanese Patent Laid-Open No. 11-48502 JP 2001-288390 A Japanese Patent Laid-Open No. 2001-179956 Japanese Patent Laid-Open No. 2002-3768 JP 2003-277653 A JP 2004-27127 A JP 2004-99657 A JP 2004-225036 A JP 2004-250519 A

  The inventors of the present invention, when using a light black ink whose pigment is carbon black and having a low content, have the aggregation state of the pigment control the characteristics of the water-soluble organic compound contained in the ink and the recording process. The knowledge that it is greatly influenced by the change was obtained. Specifically, it has been found that the following phenomenon occurs when a monochromatic image is formed on glossy paper or semi-glossy paper using the above-described conventional light black ink composition. That is, when the dots are finely connected and the ink has fluidity before being fixed to the ink receiving layer, the dots irregularly move in the surface direction of the ink receiving layer surface. As a result, adjacent dots and dots that subsequently land form an aggregate, and this causes a new phenomenon in which density unevenness that can be confirmed with the naked eye is generated in the recorded image as shown in FIG. Recognized that it will occur. Hereinafter, the above phenomenon that may occur in the light black ink is referred to as a micro beading phenomenon. The micro beading phenomenon is a new phenomenon that occurs when recording is performed with a relatively low duty, and is different from the conventional beading phenomenon. That is, the conventional beading phenomenon is a phenomenon that occurs when ink is overflowed when recording with a high duty during multi-pass recording using dark black ink using a pigment.

  Accordingly, the present inventors have studied the problem of suppressing the microbeading phenomenon that occurs in a monochromatic image using this light black ink. Specifically, structural components such as water-soluble organic compounds and surfactants contained in the ink were examined. As a result, it has been found that the microbeading phenomenon that occurs in the monochromatic image of the light black ink is solved.

  However, by using the light black ink as described above, the microbeading phenomenon of a single color image can be reduced, but it has been found that there may be a new problem in an image formed by combining the light black ink. That is, in order to improve the tone of the gray line, when a secondary color or tertiary color image of light black ink and light cyan and / or light magenta is formed, a microbeading phenomenon occurs partially. The image may become non-uniform.

  The present inventors diligently studied the microbeading phenomenon that partially occurs in secondary and tertiary images of light black and light cyan and / or light magenta. As a result, it has been found that this phenomenon can be mitigated by slowing the drying speed of the pigment on the recording medium. However, on the other hand, it has been found that when the above-described means is used, the fixability after ink is applied onto the recording medium is greatly deteriorated. Furthermore, when recording gray with high duty and high recording density, the ink cannot be absorbed inside the recording medium, resulting in “overflow” and image quality deterioration (so-called beading phenomenon). It has also been found that it creates new problems.

  Accordingly, an object of the present invention is to provide an ink set that enables good image formation in which the occurrence of both the micro beading phenomenon and the beading phenomenon is suppressed. Another object of the present invention is to provide an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus capable of forming the above-described excellent image by using such an ink set.

  The above object is achieved by the present invention described below. That is, the ink set of the present invention has a carbon black content of 0.2% by mass to 1.5% by mass and a nonionic surfactant content of 0.5% by mass to 3.0% by mass. A light black ink, a light cyan ink having a pigment content of 0.2% by mass to 1.5% by mass, and a nonionic surfactant content of 0.5% by mass to 3.0% by mass; In addition, the light black ink is a water-soluble organic compound that is solid at 25 ° C. or a liquid at 25 ° C. and has a surface tension value at 25 ° C. The water-soluble organic compound that contains a water-soluble organic compound that is 35 mN / m or more and that is liquid at 25 ° C. contained in the ink has a surface tension value of 35 at 25 ° C. N / m or more, and the total content of these water-soluble organic compounds in the light black ink is in the range of 30% by mass to 40% by mass. The light cyan ink and / or the light magenta ink is Furthermore, it contains a water-soluble organic compound that is solid at 25 ° C., or a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more, and is contained in the ink. Water-soluble organic compounds that are liquid at 25 ° C. only have a surface tension value at 25 ° C. of 35 mN / m or more, and the total content of these water-soluble organic compounds in light cyan ink and / or light magenta ink. Is in the range of 20% by mass to 30% by mass.

  In addition, an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus according to another embodiment of the present invention are characterized by using the ink constituting the ink set.

  According to the present invention, there is provided an ink set capable of forming an image with the microbeading phenomenon and the beading phenomenon suppressed. According to another embodiment of the present invention, there are provided an ink jet recording method, an ink cartridge, a recording unit, and an ink jet recording apparatus that can obtain the above-described good image by using the ink set.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention. As a result of intensive studies to solve the problems of the prior art, the inventors can obtain an excellent effect by combining a light black ink having a specific configuration with a light cyan ink and / or a light magenta ink. As a result, the present invention has been achieved. Specifically, the content of the nonionic surfactant that is a constituent component of these inks and the content of the water-soluble organic compound are controlled to be within a specific range. Further, at that time, as the water-soluble organic compound, a compound which is solid at 25 ° C. and / or a liquid which is liquid at 25 ° C. and has a specific surface tension is contained. At this time, the water-soluble organic compound that is liquid at 25 ° C. has only a surface tension at 25 ° C. of 35 mN / m or more. In the present invention, whether the state of the water-soluble organic compound at 25 ° C. is solid or liquid indicates not the mixture or the like but the state of the water-soluble organic compound alone. By forming an image using the ink having such a configuration, it is possible to provide a monochrome image, a secondary color, or a tertiary color image in which the occurrence of the microbeading phenomenon and the beading phenomenon is suppressed. The reason why the above problems can be solved by using the ink set of the present invention having the above-described configuration will be described below.

  First, the microbeading phenomenon that may occur when an image is formed on glossy paper or semi-glossy paper using light ink that contains relatively little pigment in the ink as compared with dark ink will be described. The micro beading phenomenon can be said to be a new problem peculiar to the pigment ink having a small pigment content, but the cause of this phenomenon at the time of multi-pass printing with low duty will be considered below. Multi-pass printing is a printing method in which an image is formed by scanning each color nozzle row n times for a printing area. In multi-pass printing, when the number of printing passes, which is the number of divided printing scans, increases, the printing duty per scan is reduced, and printing is performed while complementing each scan so that the image is completed n times. It can be carried out.

  FIG. 5A is a cross-sectional view schematically showing a state immediately after the first ink droplet of light ink has landed on the recording medium 90. At this time, the components 92 other than the pigment in the ink penetrate into the recording medium 90, but the pigment 91 does not penetrate into the recording medium 90 because the size is larger than the pores of the ink receiving layer on the surface of the recording medium 90. Will be present on the surface. At this time, since the pigment content in the light ink is small compared to the (dark) ink in which the pigment content in the ink is large, the number of pigments present on the surface of the recording medium 90 when the ink lands on the recording medium 90. Will be less. In this aggregate of pigments with a small number of existences, there are few water and solvent components contained in the periphery and inside, so when they first land, they will dry at an early stage when the small solvent components penetrate. On the other hand, when the content of the pigment in the ink is large, many pigments are overlapped and many solvent components are present in the vicinity and inside thereof, so that drying takes time.

  Therefore, in the pass recording using the light ink, before the ink droplet 93 in the second pass of the next landing, the surface of the recording medium 90 is dried by the penetration and diffusion of water or a water-soluble organic compound. It is thought that the surface pores are blocked with pigment particles. Due to such a mechanism, when a multi-pass image is formed, the pigment on the surface of the recording medium becomes “marked” as shown in FIG. 5B at a relatively low duty. For this reason, the ink that lands next is prevented from penetrating into the recording medium, and uneven absorption occurs, resulting in unevenness in the position of the pigment (for example, carbon black) 91 on the surface. Furthermore, even when the number of passes is increased, at the subsequent ink landing, these ink droplets move irregularly in the surface direction of the surface of the ink receiving layer, forming an aggregate of adjacent dots and new dots, Density unevenness may occur in the recorded image. In the image formed by the above process, fine unevenness of the pigment 91 occurs on the recording medium 90 as shown in FIG. Then, as shown in FIG. 5D, in the formed image, a portion where ink droplets are connected and a portion where ink droplets do not exist appear as fine mottled density unevenness that can be confirmed with the naked eye. Thus, it is presumed that the micro beading phenomenon occurs and the image quality deteriorates.

  The above microbeading phenomenon occurs in light black ink, light cyan ink, and light magenta ink when a single color image is formed with an ink having a relatively low pigment content compared to normal dark ink. It is. Among these, in particular, when forming an image with a single color, the deterioration of the image that appears specifically with light black ink with a large difference in contrast between the recording unit and the recording medium becomes noticeable. Further, even when a secondary color or tertiary color is formed using light black ink and light cyan ink and / or light magenta ink, the microbeading phenomenon occurs remarkably by the same mechanism.

  In addition, this micro beading phenomenon emphasizes high-speed fixability, and in a penetrating ink in which the surface tension of the ink is reduced using a surfactant or a penetrating water-soluble organic solvent (also called penetrant). Especially noticeable. This is because, in the above penetrating inks, the penetration speed of water and water-soluble organic solvent into the recording medium is accelerated, whereby the drying of the pigment is promoted, and the pores on the surface of the recording medium are “marked”. I think that this is because the effect of "

  From the above, it is considered that the microbeading phenomenon can be reduced by slowing the drying of the pigment on the recording medium. In this case, as a method of slowing the drying of the pigment, a method of reducing the surface tension by reducing the content of the penetrant in the ink, or a water-soluble property in the ink after the ink has landed and applied to the recording medium. In order to slow down the evaporation of an organic solvent or the like, a method of increasing the amount of a nonvolatile water-soluble organic solvent is known. However, when ink having the above-described configuration is used, the microbeading phenomenon is certainly reduced, but after recording, the penetration of water-based components toward the inside of the recording medium is delayed, so that the coloring material is dried, The time required for fixing becomes longer. For this reason, when high duty secondary color or tertiary color image formation is performed using these inks, the ink cannot be absorbed into the recording medium and the ink overflows. When this occurs, mottled unevenness occurs in the formed image (so-called beading phenomenon), and the image quality deteriorates.

  Therefore, the present inventors paid attention to the behavior of the pigment particles on the surface of the special paper such as glossy paper and semi-glossy paper, and the presence of the pigment particles by the constituent components such as the water-soluble organic compound and the surfactant in the ink. The possibility of controlling the morphology was investigated. As a result, by forming the water-soluble organic compound and the surfactant in the ink into a specific configuration, uniform and beautiful image formation without the micro-beading phenomenon and the beading phenomenon, which could not be achieved by the prior art, can be achieved. It has been found that this is possible and has led to the present invention.

  Specifically, the light black ink having the carbon black content of 0.2% by mass to 1.5% by mass constituting the ink set of the present invention is configured as follows. The content of the nonionic surfactant is 0.5% by mass to 3.0% by mass, and further the water-soluble organic compound that is solid at 25 ° C. and / or the liquid at 25 ° C. and the surface tension at 25 ° C. A water-soluble organic compound having a value of 35 mN / m or more is included. At this time, the water-soluble organic compound that is liquid at 25 ° C. has only a surface tension at 25 ° C. of 35 mN / m or more. Further, the total content of these water-soluble organic compounds in the light black ink is set in the range of 30% by mass to 40% by mass.

  Further, the light cyan ink and / or light magenta ink, which constitutes the ink set of the present invention and has a pigment content of 0.2% by mass to 1.5% by mass, specifically has the following configuration. To do. The content of the nonionic surfactant is 0.5% by mass to 3.0% by mass, and further the water-soluble organic compound that is solid at 25 ° C. and / or the liquid at 25 ° C. and the surface tension at 25 ° C. A water-soluble organic compound having a value of 35 mN / m or more is included. At this time, the water-soluble organic compound that is liquid at 25 ° C. has only a surface tension at 25 ° C. of 35 mN / m or more. Further, the total content of these water-soluble organic compounds in the light cyan ink and / or light magenta ink is configured to be in the range of 20% by mass to 30% by mass.

  Hereinafter, a process until each ink constituting the ink set of the present invention lands on a recording medium and an image is formed in the vicinity of the surface will be described. First, the process until the light black ink constituting the ink set of the present invention is landed on the recording medium and thereby a monochromatic image with reduced microbeading phenomenon is formed will be described.

  FIG. 6A is a cross-sectional view schematically showing a state immediately after the first pass of the light black ink droplet has landed on the recording medium 100. At this time, most of the aqueous component 102 other than the pigment (carbon black) 101 in the ink quickly penetrates into the recording medium 100. On the other hand, among the water-soluble organic compounds 103 constituting the light black ink, those that are liquid at 25 ° C. have high surface tension. For this reason, when the content in the ink is 30% by mass to 40% by mass, a large amount exists in the vicinity of the pigment immediately after ink landing without penetrating into the recording medium. Further, in the case of a solid at 25 ° C., solid-liquid separation occurs with the aqueous component moving into the recording medium, so that it tends to stay near the surface of the recording medium as compared with the aqueous component penetrating into the recording medium. Tend. For this reason, since the carbon black 101 retains the ink components composed of these water-soluble organic compounds in the vicinity of the pigment particles, the extreme drying until the ink droplet 104 in the second pass reaches is alleviated. Therefore, as shown in FIG. 6B, the ink droplet 104 can uniformly penetrate into the recording medium 100 after landing. The monochromatic image thus formed has uniform pigment particles on the surface of the recording medium as shown in FIG. 6C, and therefore has no microbeading phenomenon as shown in FIG. 6D. Is formed.

  With the above process, the micro beading phenomenon is reduced in a monochrome single-color image using light black ink. However, even when the light black ink as described above is used, when a secondary color or tertiary color image is formed by the combined use with the light cyan ink and / or the light magenta ink, the following new Create a challenge. That is, when an image is formed as described above, a microbeading phenomenon partially occurs and the image becomes non-uniform. This is considered due to the following causes. The carbon black 101 which is a pigment in the light black ink is not “stop” because extreme drying on the recording medium is alleviated as described above. However, it is presumed that the pigment in the light cyan ink or light magenta ink used together becomes “stop” and prevents the light black ink from being absorbed.

  As a result of intensive studies on the above problems, the inventors of the present invention need to define the configurations of the light cyan ink and the light magenta ink to be used in addition to the configuration of the light black ink as described above. It came to the conclusion that it is. The present inventors have found that the light cyan ink and / or light magenta ink used in combination with the light black ink has a configuration defined in the present invention. That is, by using the light black ink and the light cyan ink and / or light magenta ink constituting the ink set of the present invention in combination, even in the secondary color or tertiary color image formed by these, the micro beading phenomenon Can be reduced.

  Next, a process from when the light black ink and the light cyan ink and / or light magenta ink constituting the ink set of the present invention land on the recording medium until an image is formed near the surface will be described with reference to FIG. I will explain. Here, a case will be described in which each of the inks constituting the ink set of the present invention is used to form a secondary color image in the order of light cyan ink in the first pass and light black ink in the second pass. The following mechanism has no effect even if the application order of these inks is reversed. The same applies to the formation of a secondary color image using light magenta ink instead of light cyan ink, and further forming a tertiary color image using light black ink, light cyan ink, and light magenta ink.

  FIG. 7A shows a state where the light cyan ink droplet of the first pass has landed on the cross section of the recording medium 110. At this time, most of the aqueous components 112 other than the pigment in the light cyan ink quickly penetrate into the recording medium. On the other hand, since the water-soluble organic compound 113 used in the present invention is liquid, its own surface tension is high. Therefore, when the content in the ink is within the specified range of the present invention, immediately after ink landing. Exists in the vicinity of the pigment without penetrating into the medium. Also, in the case of a solid substance, it causes solid-liquid separation from the aqueous component that moves into the recording medium, and therefore tends to stay near the surface of the recording medium compared to the aqueous component that penetrates into the recording medium. is there. For this reason, since the cyan pigment 111 retains the ink components composed of these water-soluble organic compounds in the vicinity of the pigment particles, extreme drying until the landing of the light black ink droplet 114 in the second pass is alleviated. For this reason, as shown in FIG. 7B, the light black ink droplets 114 can uniformly penetrate into the recording medium after landing. Therefore, as shown in FIG. 7C, since the pigment particles are uniformly present on the surface of the recording medium, the formed image has no micro beading phenomenon as shown in FIG. 7D. Is formed.

  The effect obtained by the present invention is clearly different from the case where the content of the surfactant in the ink is simply defined. For example, when the content of the surfactant is reduced, the value of the surface tension is increased and the ink is slow to penetrate. In this case, the microbeading phenomenon is not sufficiently reduced, and the beading phenomenon occurs due to the extremely low fixability and the overflow of ink. On the other hand, when the content of the surfactant is increased, the microbeading phenomenon occurs even if good fixability is obtained, and at the same time, it is difficult to obtain sufficient performance.

  In addition to using a water-soluble organic compound having specific physical properties, the present inventors pay attention to the combination with the surfactant and the relationship between the contents, fixing the pigment as described above onto the recording medium, In view of the permeation behavior of a specific water-soluble organic solvent, the inventors have intensively studied. As a result, it has been found that the above-described behavior can be sufficiently controlled by adopting the configuration defined in the present invention for each color of the light ink used in combination. In other words, a penetration state that could not be obtained until now was obtained. Therefore, for the first time with the configuration of the present invention, it is considered that good fixing can be realized simultaneously with the reduction of the micro beading phenomenon.

  In the light black ink constituting the ink set of the present invention, the content of carbon black contained in the ink is 0.2 mass% to 1.5 mass%. The light cyan ink and light magenta ink used in combination with this have a pigment content of 0.2 mass% to 1.5 mass% in the ink. When each ink contains a pigment with a content higher than this, since the time required for drying increases due to the presence of many pigment particles, the microbeading phenomenon hardly occurs. On the other hand, the above range is preferable in order to obtain effects such as the improvement of color reproducibility with respect to dark colors such as shadow portions, the improvement of gray gradation, and the stability of gray balance, which are advantages of using light black ink. In addition, the above range is preferable in order to obtain effects such as color reproducibility in a highlight portion and reduction in graininess, which are advantages of using light cyan ink and light magenta ink.

  Furthermore, the present inventors have conducted intensive studies on the water-soluble organic compounds contained in these inks. As a result, it was found that the effect of the present invention is most exhibited when the light black ink satisfies the following two conditions. That is, it is necessary that the light black ink contains a water-soluble organic compound that is solid at 25 ° C. and / or a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more. is there. The water-soluble organic compound that is liquid at 25 ° C. needs to have only a surface tension at 25 ° C. of 35 mN / m or more. Furthermore, it has been found that the total amount of the water-soluble organic compound needs to be in the range of 30% by mass to 40% by mass. It is preferable that a water-soluble compound other than the above as a water-soluble organic compound is a liquid at 25 ° C. but has a surface tension at 25 ° C. of less than 35 mN / m, that is, a penetrating water-soluble organic solvent is present in the ink. Absent. In this case, when ink droplets land, the penetration of components other than the pigment, such as water and water-soluble organic compounds, into the recording medium becomes too high, and the drying of the pigment is promoted. This is because the degradation of image quality due to the micro beading phenomenon becomes remarkable. Moreover, it is not preferable that the total amount of the water-soluble organic compound is less than 30% by mass. In this case, when the pigment is dried quickly and recording in a single color, or when the applied amount of light cyan ink or light magenta ink is small, the difference in contrast between the pigment and the recording medium becomes large, and the visual difference due to the microbeading phenomenon occurs. Image non-uniformity stands out. Further, when the total amount of the water-soluble organic compound is larger than 40% by mass, it is not preferable because good fixability cannot be obtained, and problems such as ink ejection failure are liable to occur due to an increase in viscosity.

  In addition, the present inventors have further investigated the water-soluble organic compound contained in the light cyan ink or light magenta ink. As a result, it has been found that when the light cyan ink and light magenta ink constituting the ink set of the present invention satisfy the following two conditions, the effect of the present invention is most exhibited. That is, the ink must contain a water-soluble organic compound that is solid at 25 ° C. and / or a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more. It is. The water-soluble organic compound that is liquid at 25 ° C. needs to have only a surface tension at 25 ° C. of 35 mN / m or more. Furthermore, it has been found that the total amount of the water-soluble organic compound needs to be in the range of 20% by mass to 30% by mass. Other than the above, the water-soluble organic compound is liquid at 25 ° C., but there is a water-soluble substance whose surface tension at 25 ° C. is less than 35 mN / m, or the total amount of the water-soluble organic compound is 20% by mass. It is not preferable that it is less than. This is because when the secondary color or tertiary color is formed together with the light black ink, the pigment is quickly dried, and the image quality is significantly lowered due to the micro beading phenomenon. Further, it is not preferable that the total amount of the water-soluble organic compound is larger than 30% by mass. This is because the following phenomenon occurs when secondary or tertiary image formation is performed with light black ink in which the total amount of the water-soluble organic compound is in the range of 30% to 40% by mass. That is, in a high duty region where the amount of ink applied for each color is large, the drying speed of the pigment on the recording medium becomes too slow, resulting in overflow, and unevenness in the image due to the beading phenomenon. Hereinafter, specific components that can be used for each ink constituting the ink set of the present invention will be described.

[Surfactant]
Each ink constituting the ink set of the present invention is characterized by containing a nonionic surfactant in a range of 0.5 mass% to 3.0 mass%. When the content is less than 0.5% by mass, good fixability cannot be obtained. When the content is more than 3.0% by mass, the ink ejection properties from the resting state are adversely affected. . As the nonionic surfactant used in the present invention, those having an ethylene oxide group or acetylene glycol surfactants are preferable.

  Examples of the nonionic surfactant having an ethylene oxide group include compounds represented by the following structural formulas (1) to (4).

（但し、上記構造式（１）中、Ｒはアルキル基を表し、ｎは整数を表す。）

(In the structural formula (1), R represents an alkyl group, and n represents an integer.)

（但し、上記構造式（２）中、Ｒはアルキル基を表し、ｎは整数を表す。）

(In the structural formula (2), R represents an alkyl group, and n represents an integer.)

（但し、上記構造式（３）中、Ｒは水素原子又はアルキル基を表し、ｍ及びｎは、夫々整数を表す。）

(In the structural formula (3), R represents a hydrogen atom or an alkyl group, and m and n each represents an integer.)

（但し、構造式（４）中、ｍ及びｎは、夫々整数を表わす。）

(In the structural formula (4), m and n each represents an integer.)

  In the structural formula (1), R is preferably an alkyl group having 8 to 21 carbon atoms. R may be linear or branched. n is preferably an integer of 5 to 40. It is also possible to use a mixture of two or more compounds having different values of R and / or n.

  In the structural formula (2), R is preferably an alkyl group having 8 to 21 carbon atoms. R may be linear or branched. n is preferably an integer of 5 to 40. It is also possible to use a mixture of two or more compounds having different values of R and / or n.

  In the structural formula (3), m is preferably an integer of 1 to 10. n is preferably an integer of 1 to 10. In addition, m means the number of ethylene oxide units, n means the number of propylene oxide units, and any of a block copolymer, an alternating copolymer, and a random copolymer may be used. A mixture of two or more compounds having different values of m and / or n can also be used.

  In the structural formula (4), m is preferably an integer of 1 to 10. n is preferably an integer of 1 to 10. A mixture of two or more compounds having different values of m and / or n can also be used.

  When the nonionic surfactant having the ethylene oxide group is used, the effects of the present invention are sufficiently obtained. Among the above, the use of the acetylene glycol surfactant represented by the structural formula (4) is most preferable because a particularly excellent effect is obtained in fixability. Furthermore, it is particularly preferable that the value of m + n in the structural formula (4) is 3 or more. When the value of m + n is less than 3, it is not preferable because the hydrophobicity is large and the solubility in ink is low, and the ink is easily separated.

[Water-soluble organic compounds]
The light black ink, light cyan ink, and light magenta ink constituting the ink set of the present invention are required to contain the following water-soluble organic compounds. That is, it includes a water-soluble organic compound that is solid at 25 ° C. and / or a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more. The water-soluble organic compound that is liquid at 25 ° C. has only a surface tension at 25 ° C. of 35 mN / m or more. Further, the light black ink has a total amount of the water-soluble organic compound of 30% by mass to 40% by mass, and the light cyan ink and the light magenta ink have a total amount of the water-soluble organic compound of 20% by mass to 30% by mass. Range.

  Examples of water-soluble organic compounds that are solid at 25 ° C. include moisturizing solids such as urea, thiourea, ethyleneurea, trimethylolpropane, and trimethylolethane, and polyethylene glycol having an average molecular weight of 1,000 or more. These are preferably contained in the range of 0.1% by mass to 20.0% by mass based on the total mass of the ink, and more preferably in the range of 3.0% by mass to 10.0% by mass. Among these, it is particularly preferable to contain urea, thiourea, ethylene urea, trimethylolpropane, trimethylolethane, or polyethylene glycol having an average molecular weight of 1,000 or more. This is because even if these compounds are contained in a relatively large amount in the ink, reliability such as adhesion is hardly impaired. In addition, when saccharides are used as the water-soluble organic compound that is solid at 25 ° C., the microbeading phenomenon can be solved, but the sticking property deteriorates and is not suitable for practical use. Therefore, in this invention, it examined using water-soluble organic compounds other than saccharides.

When selecting a water-soluble organic compound that is liquid at 25 ° C., the one having a surface tension value at 25 ° C. of 35 mN / m or more is selected, and the content of each water-soluble organic compound is determined in the present invention. It must be within the specified range. As long as the above conditions are satisfied, the water-soluble organic compound used for preparing each ink constituting the ink set of the present invention is not particularly limited, and for example, the following can be used.
Alkyl alcohols. Amides. Ketones or keto alcohols. Ethers such as tetrahydrofuran and dioxane. Polyalkylene glycols. Alkylene glycols such as triethylene glycol and propylene glycol; Lower alkyl ethers of polyhydric alcohols such as triethylene glycol monobutyl ether. Polyhydric alcohols such as glycerin. N-methyl-2-pyrrolidone, 2-pyrrolidone and the like. Among them, as the water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more, it is particularly preferable to use glycerin, triethylene glycol, propylene glycol, or the like.

  Moreover, it is preferable to use deionized water. The content of water contained in the ink is preferably in the range of 40% by mass to 70% by mass based on the total mass of the ink.

[Pigment]
The light black ink constituting the ink set of the present invention contains carbon black. As the carbon black used in the present invention, for example, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used.

  Specifically, for example, the following commercially available products can be used. Ray Van: 7000, 5750, 5250, 5000 ULTRA, 3500, 2000, 1500, 1250, 1200, 1190 ULTRA-II, 1170, 1255 (above Colombia). Black Pearls L, Legal: 400R, 330R, 660R, Mogulu L, Monak: 700, 800, 880, 900, 1000, 1100, 1300, 1400, 2000, Vulcan XC-72R (above, manufactured by Cabot). Color Black: FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex: 35, U, V, 140U, 140V, Special Black: 6, 5, 4A, 4 (above, manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (above, manufactured by Mitsubishi Chemical). Carbon black newly prepared for the present invention can also be used. However, the present invention is not limited to these, and any conventionally known carbon black can be used.

  Moreover, there is no restriction | limiting in particular in the pigment used for the light cyan ink or the light magenta ink which can be used for the structure of the ink set of this invention. As an example, when the color index (CI) number of an organic pigment is indicated, for example, the following can be used. Of course, it is not limited to these, and other organic pigments may be used. C. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217 and the like. In addition, C.I. I. Pigment Red 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272. C. I. Pigment violet 19. C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64.

<Pigment dispersion>
The pigments listed above are preferably added to the ink as a pigment dispersion obtained by dispersing the pigment in an aqueous medium using a resin or the like as a dispersant. Below, the pigment dispersion liquid which can be used in this invention is demonstrated. The carbon black used in the present invention is preferably added to the ink as a pigment dispersion obtained by dispersing it in an aqueous medium with a dispersant or the like. The pigment used in the present invention is preferably a resin dispersed pigment dispersed with a resin or a microcapsule pigment. In addition, a surfactant-dispersed pigment dispersed in an aqueous medium using a surfactant as a dispersing agent, or a self-dispersing pigment imparted with dispersibility by introducing a hydrophilic group on the surface of pigment particles It is good also as what adds.

(Resin dispersion type pigment)
First, the resin dispersed pigment will be described. In addition, the resin described below can be used as a dispersant, or can be used as a resin added to the surfactant-dispersed pigment or the self-dispersed pigment. Here, as the resin, either a natural polymer or a synthetic polymer can be used. In the present invention, it is preferable to use a synthetic polymer such as a water-soluble polymer. The production method of the synthetic polymer is not particularly limited, and for example, it is produced by reacting a monomer having an ionic group and another polymerizable monomer in a non-reactive solvent using a catalyst as necessary. can do.

  Specifically, the resin includes, for example, a block copolymer, a random copolymer, and a graft copolymer composed of at least two monomers (of which at least one is a hydrophilic monomer) selected from the following group. Polymers and salts thereof can be used. Styrene, vinyl naphthalene, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, maleic acid, itaconic acid, fumaric acid, vinyl acetate, vinyl alcohol, vinyl pyrrolidone, acrylamide, and derivatives thereof .

  In the present invention, a styrene / acrylic polymer compound obtained by polymerizing a monomer having an ionic group and a styrene monomer as essential components is particularly preferably used as a dispersant. Alternatively, it is particularly preferable to use an ionic group-containing acrylic polymer compound obtained by polymerizing a monomer having an ionic group and a (meth) acrylic acid ester monomer having 5 or more carbon atoms as essential components.

  In the present invention, for the dispersion of the pigment, for example, a disperser such as a paint shaker, a sand mill, an agitator mill, or a three roll mill, a high-pressure homogenizer such as a microfluidizer, nanomizer, or optimizer, an ultrasonic disperser, or the like is used. Can do. Of course, any dispersion method that is generally used can be used.

(Microcapsule type pigment)
The microcapsule type pigment will be described. Examples of the method of coating the pigment with an organic polymer and microencapsulating include a chemical production method, a physical production method, a physicochemical production method, and a mechanical production method. Specifically, interfacial polymerization method, in-situ polymerization method, submerged cured coating method, coacervation (phase separation) method, submerged drying method, melt dispersion cooling method, air suspension coating method, spray drying method , Acid precipitation method, phase inversion emulsification method and the like.

  Organic materials and nonionic organic polymers can be used as the material constituting the wall membrane material of the microcapsule. Specific examples of the organic polymers include the following. Polyamide, polyurethane, polyester, polyurea, epoxy resin, polycarbonate, urea resin, melamine resin, phenol resin. Polysaccharides, gelatin, gum arabic, dextran, casein, protein, natural rubber. Carboxy polymethylene, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride. Cellulose, ethyl cellulose, methyl cellulose, nitrocellulose, hydroxyethyl cellulose, cellulose acetate. Polyethylene, polystyrene, (meth) acrylic acid polymer or copolymer, (meth) acrylic acid ester polymer or copolymer, (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene- ( (Meth) acrylic acid copolymer, styrene-maleic acid copolymer. Examples include sodium alginate, fatty acid, paraffin, beeswax, water wax, hardened beef tallow, carnauba wax, albumin and the like. Among these, it is preferable to use organic polymers having an anionic group such as a carboxylic acid group or a sulfonic acid group.

  Specific examples of the nonionic organic polymer include the following. Examples thereof include polyvinyl alcohol, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate or their (co) polymer, and a cationic ring-opening polymer of 2-oxazoline. Among these, a completely saponified product of polyvinyl alcohol is preferable because it has low water solubility and is easily soluble in hot water but hardly soluble in cold water.

  When the phase inversion method or the acid precipitation method is selected as the microencapsulation method, an anionic organic polymer is used as the organic polymer constituting the wall membrane material of the microcapsule. The phase inversion method is a composite or composite of an anionic organic polymer having self-dispersibility or solubility in water and a dispersible color material, or a dispersible color material, a curing agent, and an anionic property. A mixture with organic polymers is used as an organic solvent phase. Then, water is introduced into the organic solvent phase or the organic solvent phase is introduced into water and microencapsulated while self-dispersing (phase inversion emulsification). In the phase inversion method, there is no problem even if microcapsules are produced by adding a water-soluble organic compound or additive used for the ink to the organic solvent phase. In particular, it is preferable to add a water-soluble organic compound used for the ink because a dispersion liquid directly used for the ink can be directly produced.

  The acid precipitation method is as follows. A step of kneading, in an aqueous medium, a material obtained by neutralizing a part or all of an anionic group of an organic polymer containing an anionic group with a basic compound and a dispersible colorant. Then, a step of causing the pH of the mixture to be neutral or acidic with an acidic compound and precipitating an organic polymer containing an anionic group and fixing it to the pigment is performed to obtain a water-containing cake. Next, this water-containing cake is microencapsulated by neutralizing part or all of anionic groups with a basic compound. According to the acid precipitation method, an anionic microcapsule-type color material that is fine and contains a large amount of color material can be produced.

  Specific examples of the water-soluble organic compound used in the production of the microcapsule-type color material as described above can include the following. Alkyl alcohols such as methanol, ethanol, propanol and butanol; Aromatic hydrocarbons such as benzol, triol, and xylol. Esters such as methyl acetate, ethyl acetate and butyl acetate. Chlorinated hydrocarbons such as chloroform and ethylene dichloride. Ketones such as acetone and methyl isobutyl ketone. Ethers such as tetrahydrofuran and dioxane. Examples thereof include cellosolves such as methyl cellosolve and butyl cellosolve.

  By performing centrifugation or filtration on the microcapsule type color material produced by the method as described above, the microcapsule type color material can be separated from the water-soluble organic compound. Furthermore, it can also be set as the target microcapsule type color material by mixing with water and a required water-soluble organic compound, stirring, and redispersing.

(Polymer-bonded self-dispersing pigment)
The polymer-bonded self-dispersing pigment will be described. A polymer-bonded self-dispersing pigment is obtained by reacting a functional group chemically bonded to the surface of pigment particles directly or through another atomic group with a copolymer of an ionic monomer and a hydrophobic monomer. It is preferable to use what is contained. This can change the copolymerization ratio of the ionic monomer and the hydrophobic monomer, which are the materials of the copolymer used for modifying the surface, as appropriate, and the hydrophilicity of the modified pigment can be changed arbitrarily. It is because it can be adjusted to. Moreover, since the kind of ionic monomer and hydrophobic monomer and the combination of both can be arbitrarily changed, various characteristics can be imparted to the surface of the pigment particles.

  The dispersed particle diameter of the pigment in the pigment dispersion prepared by the method described above is preferably 10 nm to 500 nm, particularly 30 nm to 300 nm. By setting the dispersed particle diameter in the above-described range, stable dispersion stability and the like can be obtained.

[Other ingredients]
In addition to the above components, each ink constituting the ink set of the present invention includes a surfactant, a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, as necessary. Various additives such as an evaporation accelerator and a chelating agent may be contained.

  In addition to the nonionic surfactant that is an essential component of the ink used in the present invention, the surfactant is used in combination with these surfactants in order to adjust the surface tension and improve the ejection properties. An agent may be used. The content of these compounds in the ink is preferably in the range of 0.05% by mass to 5% by mass based on the total mass of the ink. More preferably, the content is 0.1% by mass to 2% by mass.

[Ink characteristics]
The ink constituting the ink set of the present invention having the constituent components described above preferably has a characteristic that can be favorably ejected from the recording head, particularly when used in an ink jet recording method. For this reason, the ink has, for example, a viscosity of 1 mPa · s to 15 mPa · s, further 1 mPa · s to 5 mPa · s, and a surface tension of 25 mN / m to 25 mN / m. It is preferably 50 mN / m or less. It is preferable that the viscosity of the ink is in the above-described range because normal ejection can be performed in ink jet recording, and the penetration into the recording medium is fast due to the viscosity resistance, and there is no problem in terms of fixability. When the surface tension of the ink is in the above range, after ejecting ink droplets in ink jet recording, the force to pull back the meniscus is strong, or conversely, the force to pull back is relatively strong when the meniscus protrudes. . For this reason, it is preferable because problems such as embedding bubbles and causing the orifice portion to get wet and cause twisting are preferable.

[Ink set]
The ink set used in the present invention is used in the following forms, and these are substantially referred to as “ink set”. An ink cartridge containing a combination of light black ink, light cyan ink and / or light magenta ink, and other inks as required. An ink cartridge in which the above-described combination of inks is integrally stored. Or, an ink cartridge with a head in which a combination of these inks is stored, or an ink cartridge that can be attached to and detached from the recording apparatus. In any case, in the present invention, the characteristics of a single unit such as the light black ink constituting the ink set of the present invention are described first with respect to other inks used (in the ink jet recording apparatus or as an ink cartridge). As long as it is defined. Therefore, the present invention is not limited to the above form, and any modification form may be used. Examples of the other ink include cyan ink, magenta ink, yellow ink, black ink, red ink, green ink, blue ink, orange ink, and violet ink.

<Inkjet recording method and inkjet recording apparatus>
The ink set of the present invention is used in an ink jet recording head, and is effective as an ink cartridge for storing each ink or a set of ink for filling the ink cartridge. In particular, the effect of using the ink set of the present invention is excellent in bubble jet (registered trademark) recording heads, recording units, and ink jet recording apparatuses, among other ink jet recording methods.

  For the typical configuration and principle of the ink jet system, for example, the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is used. Is preferred. This method can be applied to both a so-called on-demand type and a continuous type. In particular, in the case of the on-demand type, a rapid temperature rise exceeding the nucleate boiling corresponding to the recorded information is applied to the electrothermal transducer disposed corresponding to the sheet or liquid path holding the ink. Apply at least one drive signal to be applied. As a result, thermal energy is generated in the electrothermal transducer and the film is boiled on the heat acting surface of the recording head. As a result, it is effective because it corresponds to this drive signal on a one-to-one basis and bubbles in the ink can be formed. By the growth and contraction of the bubbles, ink is ejected through the ejection opening to form at least one droplet. It is more preferable that the drive signal has a pulse shape, because the bubble growth and contraction is performed immediately and appropriately, and thus ink discharge with particularly excellent responsiveness can be achieved. As this pulse-shaped drive signal, those described in US Pat. Nos. 4,463,359 and 4,345,262 are suitable. Further excellent recording can be performed by employing the conditions described in US Pat. No. 4,313,124 of the invention relating to the temperature rise rate of the heat acting surface.

  The configuration of the recording head includes a combination of a discharge port, a liquid path, and an electrothermal transducer (linear liquid flow path or right-angle liquid flow path) as disclosed in the above specifications, It is also effective as a configuration arranged in the bending region. Such a configuration is disclosed in US Pat. No. 4,558,333 and US Pat. No. 4,459,600. In addition, the present invention is also effective for a configuration (JP-A-59-123670, etc.) in which a common discharge hole is used as a discharge portion of the electrothermal converter for a plurality of electrothermal converters. . Furthermore, even when a full-line type recording head having a length corresponding to the width of the maximum recording medium that can be recorded by the recording apparatus is used, the above-described effects can be more effectively exhibited. Specifically, either a configuration satisfying the length by a combination of a plurality of recording heads as disclosed in the above specification or a configuration as a single recording head formed integrally may be used.

  In addition, a replaceable chip type recording head that can be electrically connected to the apparatus and supplied with ink from the apparatus by being attached to the recording apparatus, or a cartridge integrally provided in the recording head The present invention is also effective when a type of recording head is used.

  FIG. 1 shows an example of an ink jet recording apparatus. In FIG. 1, reference numeral 61 denotes a blade as a wiping member, one end of which is held and fixed by a blade holding member, and forms a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head 65 and is held in a form protruding in the moving path of the recording head 65.

  Reference numeral 62 denotes a cap on the projection port surface of the recording head 65, which is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, contacts the ink ejection port surface, and performs capping. The structure to perform is provided. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61 and, like the blade 61, is held in a form protruding in the moving path of the recording head 65. The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the ink absorber 63 remove moisture, dust, and the like from the ejection port surface. In addition, a recovery unit that restores the original discharge performance of the ink of the print head by sucking the ink etc. of each ink discharge port of the print head by a pump (not shown) through the cap is doing.

  Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording medium facing the discharge port surface where the discharge port is arranged. Reference numeral 66 denotes a movement of the recording head 65 by mounting the recording head 65. It is a carriage for performing. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording area and its adjacent area can be moved by the recording head 65. 51 is a paper feed section for inserting a recording medium, and 52 is a paper feed roller driven by a motor (not shown).

  With these configurations, the recording medium is fed to a position facing the discharge port surface of the recording head 65, and is discharged to a paper discharge portion provided with a paper discharge roller 53 as recording progresses. In the above configuration, when the recording head 65 finishes recording and returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port of the recording head 65 is wiped. When the cap 62 is in contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as that at the time of wiping described above. As a result, the ejection port surface of the recording head 65 is wiped even during this movement. The above-mentioned movement of the recording head to the home position is not only at the end of recording or at the time of ejection recovery, but also to the home position adjacent to the recording area at a predetermined interval while the recording head moves the recording area for recording. Then, the wiping is performed with this movement.

  FIG. 2 is a view showing an example of a cartridge 45 containing a member for supplying ink to the recording head, for example, ink supplied via a tube. Here, reference numeral 40 denotes a container, for example, a bag, which stores ink for supply, and a rubber stopper 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the bag 40 can be supplied to the head. Reference numeral 44 denotes an absorber that receives waste ink. The container 40 preferably has a liquid contact surface formed with polyolefin, particularly polyethylene.

<Ink cartridge>
An ink cartridge suitable for performing recording using the ink of the present invention includes an ink cartridge having an ink containing portion in which these inks are contained. Specific examples of ink cartridges suitable for recording using the ink of the present invention are shown below.

  FIG. 3 is a schematic explanatory view and a sectional view of a liquid storage container which is an ink cartridge suitable for performing recording using the ink of the present invention. The liquid storage container is connected to the atmosphere through the atmosphere communication port 122 in the upper part, communicates with the ink supply port in the lower part, and stores a negative pressure generation member storage chamber 134 that stores a negative pressure generation member therein, and stores liquid ink. It is partitioned by a partition wall 138 into a substantially sealed liquid storage chamber 136. The negative pressure generating member storage chamber 134 and the liquid storage chamber 136 are connected to the communication hole 140 formed in the partition wall 138 in the vicinity of the bottom of the liquid storage container and to facilitate the introduction of the atmosphere into the liquid storage chamber during the liquid supply operation. Communication is performed only through the air introduction groove (atmosphere introduction path) 150. A plurality of ribs are integrally formed on the upper wall of the liquid storage container defining the negative pressure generating member storage chamber 134 so as to protrude inside, and are stored in the negative pressure generating member storage chamber 134 in a compressed state. It is in contact with the negative pressure generating member. By this rib, an air buffer chamber is formed between the upper wall and the upper surface of the negative pressure generating member. The ink supply cylinder provided with the liquid supply port 124 is provided with a pressure contact body 146 having a higher capillary force and a higher physical strength than the negative pressure generating member, and is in pressure contact with the negative pressure generating member.

  In the negative pressure generating member storage chamber of the present embodiment, two capillaries of a first negative pressure generating member 132B and a second negative pressure generating member 132A made of olefin resin fibers such as polyethylene are used as the negative pressure generating member. Houses a force-generating negative pressure generating member. Reference numeral 132C denotes a boundary layer between the two negative pressure generating members, and an intersecting portion of the boundary layer 132C with the partition wall 138 has an air introduction groove (atmosphere introduction path) in a posture when the liquid storage container is used with the communication portion downward. ) It exists above the upper end of 150. Further, the ink accommodated in the negative pressure generating member exists above the boundary layer 132C as indicated by the ink level L.

<Recording unit>
The recording unit used in the present invention is not limited to the one in which the head and the ink cartridge are separated as described above, but can be suitably used for those in which they are integrated as shown in FIG. In FIG. 4, reference numeral 70 denotes a recording unit, in which an ink storage portion that stores ink, for example, an ink absorber, is stored. The ink in the ink absorber is supplied from a head portion 71 having a plurality of orifices. It is configured to be ejected as ink droplets. It is preferable to use polyurethane or polypropylene as the material of the ink absorber. Alternatively, a structure may be used in which the ink container is an ink bag with a spring or the like inside without using an ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere. In the present invention, it is preferable to add recovery means for the recording head, preliminary auxiliary means, etc. provided as the configuration of the recording apparatus to be applied, because the effects of the present invention can be further stabilized. . Specifically, capping means for the recording head, cleaning means, pressure or suction means, electrothermal converter or preheating means using a heating element different from this, or a combination thereof, and recording This is a preliminary discharge mode in which another discharge is performed.

<Recording medium>
In the image forming method using the ink set of the present invention, but not limited thereto, a recording medium having a coating layer with ink as a receiving layer on at least one surface of various substrates such as paper and resin film, etc. It is preferable to use it. In particular, when the recording medium has a coating layer on the surface and glossy paper or semi-glossy paper configured to exhibit glossiness, a remarkable effect is obtained. Examples of such a recording medium include a recording medium having a coating layer for receiving ink on at least one surface containing at least a hydrophilic polymer and / or an inorganic porous material.

  There are various types of recording media having a coating layer that accepts ink depending on the surface state, the thickness of the coating layer, the size of the pores that absorb ink, the difference in the material constituting the ink absorption layer, and the type of substrate. There are various things. For example, glossy paper or glossy film having a high surface gloss, fine glossy paper or semi-glossy paper whose surface gloss is adjusted by processing or the like can be used. In the present invention, the effects of the present invention are particularly remarkably exhibited by using glossy paper having sufficient gloss among the recording media described above or semi-glossy paper having a surface treated with silk or the like. Therefore, it is preferable.

  For the ink receiving layer of the recording medium described above, a hydrophilic polymer or an inorganic porous material can be used. Specifically, the following can be used as the hydrophilic polymer, for example. Starch. Carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose. Alginic acid, gelatin. Polyvinyl alcohol, polyvinyl acetal, polyethylene oxide. Sodium polyacrylate, cross-linked polyacrylic acid, polyvinyl methyl ether, polystyrene sulfonic acid, quaternary polyvinyl pyridine, polyacrylamide, polyvinyl pyrrolidone, polyamine. Water-based urethane resin, water-soluble acrylic resin, water-soluble epoxy compound, water-soluble polyester, etc. In addition, a modified product of the polymer, for example, an ion-modified product such as cation-modified polyvinyl alcohol and cation-modified polyvinyl pyrrolidone can be used. Specific examples of the inorganic porous material include the following. Examples include silica gel, alumina, zeolite, and porous glass.

  In the present invention, among glossy paper and semi-glossy paper, a so-called gap type recording medium having pores produced by combining the above-mentioned materials is used, assuming that the ink permeation rate and ink absorption capability are sufficient. It is preferable. Further, in order to obtain excellent image glossiness, it is necessary to have sufficient ink absorption capability, and therefore, the recording medium is fine and has a sufficient thickness of the ink receiving layer to absorb ink. Is preferably used. The recording medium having such characteristics preferably has a pore radius of the ink receiving layer of 10 nm to 50 nm, further 20 nm or less, and a thickness of the ink receiving layer of 10 μm to 40 μm. The pore radius of the ink receiving layer of the recording medium is generally smaller than that of the pigment used in the present invention. For this reason, when the ink is applied to the recording medium, the liquid component in the ink penetrates into the recording medium, that is, the pores of the ink receiving layer, but the pigment aggregates on the surface of the recording medium.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples as long as the gist thereof is not exceeded. In the text, “parts” and “%” are based on mass unless otherwise specified. In addition, “remaining” in the table refers to a remaining amount obtained by subtracting each component from 100% of the entire ink.

(Preparation of carbon black dispersion)
10 parts of carbon black having a specific surface area of 210 m ² / g, DBP oil absorption of 74 ml / 100 g, 20 parts of a 10% sodium hydroxide neutralized aqueous solution of a styrene-acrylic acid copolymer having an acid value of 200 and a weight average molecular weight of 10,000, ions 70 parts of exchange water was mixed. This was dispersed for 3 hours using a batch type vertical sand mill, then coarse particles were removed by centrifugal separation, and further filtered under pressure with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm. A black pigment dispersion having a concentration of 10% by mass was obtained.

(Preparation of cyan pigment dispersion)
10 parts of a pigment (CI Pigment Blue 15: 3), 20 parts of a 10% sodium hydroxide neutralized aqueous solution of a styrene-acrylic acid copolymer having an acid value of 200 and a weight average molecular weight of 10,000, and 70 parts of ion-exchanged water Were mixed. This was dispersed for 3 hours using a batch type vertical sand mill, then coarse particles were removed by centrifugation, and further filtered under pressure with a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to obtain a pigment concentration. A 10% by weight cyan pigment dispersion was obtained.

(Preparation of magenta pigment dispersion)
10 parts of a pigment (CI Pigment Red 122), 20 parts of a 10% sodium hydroxide neutralized aqueous solution of a styrene-acrylic acid copolymer having an acid value of 200 and a weight average molecular weight of 10,000, and 70 parts of ion-exchanged water are mixed. did. This was dispersed for 3 hours using a batch type vertical sand mill, then coarse particles were removed by centrifugation, and further filtered under pressure with a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm to obtain a pigment concentration. A 10% by mass magenta pigment dispersion was obtained.

[Water-soluble organic compounds]
Next, the state at 25 ° C. of the water-soluble organic compounds used in the inks of the ink sets of Examples and Comparative Examples and the surface tension at 25 ° C. of those which were liquid were measured. The results are shown in Table 1. For measuring the surface tension, an automatic surface tension measuring device (trade name: CPVP-Z; manufactured by Kyowa Interface Chemical Co., Ltd.) was used.

[Preparation of ink]
The ink set of the present invention is a combination of light black ink and light cyan ink and / or light magenta ink. In the following example, an ink set of three colors of light black ink, light cyan ink, and light magenta ink is an object of the present invention. The present invention is also applied to an ink set including one or more other inks in addition to these combinations. Using each of the pigment dispersions prepared above, the components listed in Tables 2 to 4 were weighed, sufficiently dissolved and stirred, and pressure-filtered with a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm. Inks used in Examples and Comparative Examples were prepared.

[Evaluation]
The light black ink (LBk), light cyan ink (LC), and light magenta ink (LM) prepared above were combined as shown in Table 5 to obtain ink sets of Examples 1 to 7 and Comparative Examples 1 to 7. Then, using these ink sets, a gray tertiary color image such that a ^* = b ^* = 0 was formed and evaluated. The evaluation was performed by forming an image using an inkjet recording apparatus BJF-900 having an on-demand type multi-recording head that ejects ink by applying thermal energy to the ink in accordance with a recording signal.

(Microbeading phenomenon and beading phenomenon)
Using each of the ink sets and the ink jet recording apparatus described above, a tertiary color image pattern of 10 to 150% was recorded in 8 passes on Canon ink jet paper SG-101. The micro-beading phenomenon of the formed tertiary color image and whether or not the beading phenomenon occurred was evaluated according to the following criteria. The evaluation results are summarized in Table 6.

〔Evaluation results〕
A: The micro-beading phenomenon in the low duty part and the beading phenomenon in the high duty part cannot be confirmed visually or enlarged 10 times, and the formed image is uniform.
B1: Although fine color unevenness of the image due to the occurrence of the micro beading phenomenon can be visually recognized in the low duty portion, it is at a level causing no problem in image performance.
B2: Although fine color unevenness of the image due to the occurrence of the micro beading phenomenon can be visually recognized in the high duty portion, it is at a level with no problem in image performance.
C1: The occurrence of the micro beading phenomenon is noticeable even in the low duty portion, and the formed image is uneven and the color unevenness is noticeable.
C2: The occurrence of a beading phenomenon is noticeable visually at a high duty portion, the formed image is non-uniform, and the color unevenness is conspicuous.

It is a perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view of an ink cartridge. It is a schematic explanatory drawing of the ink cartridge suitable for recording using the ink of this invention. It is a perspective view which shows an example of a recording unit. It is a figure which illustrates typically a mode observed from the section, when light ink lands on a recording medium and a micro beading phenomenon occurs. It is a figure for demonstrating typically a mode that it observed from the cross section when a light black ink droplet landed on a recording medium. FIG. 5 is a diagram for schematically explaining a state observed from a cross section when an ink droplet has landed on a recording medium when a secondary color image is formed with light cyan ink and light black ink constituting an ink set.

Explanation of symbols

40: Ink bag 42: Plug 44: Ink absorber 45: Ink cartridge 51: Paper feed unit 52: Paper feed roller 53: Paper discharge roller 61: Blade 62: Cap 63: Ink absorber 64: Ejection recovery unit 65: Recording Head 66: Carriage 67: Guide shaft 68: Motor 69: Belt 70: Recording unit 71: Head unit 72: Atmospheric communication port 90: Recording medium 91: Pigment 92: Aqueous component other than pigment in ink 93: Ink droplet 100: Recording medium 101: Carbon black 102: Aqueous component mainly composed of water 103: Aqueous component mainly composed of a water-soluble organic compound used in the present invention 104: Ink droplet 110: Recording medium 111: Cyan pigment 112: Light cyan ink Water-based component 113 containing water as a main component: water-soluble organic compound in light cyan ink as a main component Water component 114: Light black ink drop 115: Light black pigment 122: Air communication port 124: Liquid supply port 132A: Second negative pressure generating member 132B: First negative pressure generating member 132C: First negative pressure generating member Boundary layer 134: negative pressure generating member storage chamber 136: liquid storage chamber 138: partition wall 140: communication hole 146: pressure contact body 150: atmosphere introduction groove (atmosphere introduction path)
L: Liquid-gas interface

Claims (10)

Light black ink having a carbon black content of 0.2 mass% to 1.5 mass% and a nonionic surfactant content of 0.5 mass% to 3.0 mass%, and a pigment content A combination of light cyan ink and / or light magenta ink having an amount of 0.2% to 1.5% by mass and a nonionic surfactant content of 0.5% to 3.0% by mass. An ink set,
The light black ink further includes a water-soluble organic compound that is solid at 25 ° C. and / or a water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more, and The water-soluble organic compound that is liquid at 25 ° C. contained in the ink has only a surface tension value of 25 mN / m or more at 25 ° C., and all the water-soluble organic compounds in the light black ink are contained in the ink. The content is in the range of 30% by mass to 40% by mass,
The light cyan ink and / or the light magenta ink are further water-soluble organic compounds that are solid at 25 ° C. and / or water-soluble that are liquid at 25 ° C. and have a surface tension value at 25 ° C. of 35 mN / m or more. The water-soluble organic compound that contains an organic compound and is liquid at 25 ° C. contained in the ink has only a surface tension value at 25 ° C. of 35 mN / m or more. An ink set, wherein the total content of light cyan ink and / or light magenta ink is in the range of 20% by mass to 30% by mass.   The ink set according to claim 1, wherein the nonionic surfactant has an ethylene oxide group.   The ink set according to claim 1, wherein the nonionic surfactant is an acetylene glycol surfactant.   The ink set according to claim 1, wherein the water-soluble organic compound that is solid at 25 ° C. is not a saccharide.   The water-soluble organic compound that is solid at 25 ° C is any one of urea, thiourea, ethyleneurea, trimethylolpropane, trimethylolethane, or polyethylene glycol having an average molecular weight of 1,000 or more. The ink set according to any one of the above.   6. The water-soluble organic compound that is liquid at 25 ° C. and has a surface tension value at 25 ° C. of 35 mN / m or more is any one of glycerin, triethylene glycol, and propylene glycol. The ink set according to item 1.   An ink jet recording method for recording on a recording medium by ejecting ink by an ink jet recording method, wherein the ink constituting the ink set according to any one of claims 1 to 6 is used as the ink. Inkjet recording method.   An ink cartridge comprising an ink container for containing ink, wherein the ink is an ink constituting the ink set according to any one of claims 1 to 6.   7. A recording unit comprising an ink containing portion for containing ink and a recording head for ejecting the ink, wherein the ink is an ink constituting the ink set according to any one of claims 1 to 6. A recording unit characterized by being.   The ink which comprises the ink set of any one of Claims 1 thru | or 6 in the inkjet recording device provided with the ink accommodating part which accommodates ink, and the recording head for discharging this ink. An ink jet recording apparatus characterized by the above.

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